The present invention relates to sample injection apparatus, and more particularly, relates to multiple function sample valving apparatus for a Probe-In-Loop (PIL) sample injection assembly for liquid chromatographic analysis.
High Pressure Liquid Chromatography (HPLC) is a well known conventional technique in which liquid samples to be analyzed are injected under high pressure into a stream of solvent flowing through a chromatographic column. The sample size to be injected is usually several microliters in volume, but it may vary in size from less than 1 microliter up to 100 microliters or more. The pressure of the solvent stream into which the samples are injected may vary from less than 1000 psi up to 6000 psi or more.
Advances in Life Sciences, particularly in genomics and proteomics, have greatly increased the potential number of reactions and analyses that must be performed by the biotechnology and pharmaceutical industries. Thus, it is frequently necessary to analyze large numbers of samples routinely, even though the samples are available only in small quantities because they are difficult to isolate.
These tasks were formerly reserved for automatic sample injection devices made use of conventional 6-port sample injection valves with a sample loop which must be completely filled with the sample fluid. Typical of such devices are disclosed U.S. Pat. No. 3,918,913 to Stevenson and Coffey. While these designs provide high volumetric precision of the sample (typically in the range of 0.05-0.5% Relative Standard Deviation (RSD)), one problem associated with these xe2x80x9cComplete-Loop Injectionxe2x80x9d systems is that they required an appreciable excess of sample to fill the sample loop reliably. Typically, four to five times the capacity of the sample loop are necessary for a reliable fill. Moreover, the excess sample liquid remaining in the connecting tubing between sample vial and valve would be discarded to make way for the next sample.
To address these deficiencies, micro syringe metering devices were employed to draw up a sample from a vial and introduce it into an injection valve with little or no loss of sample. Examples of these designs are U.S. Pat. No. 3,916,692 to Abraham et al.; U.S. Pat. No. 3,961,534 to Gundelfinger, and U.S. Pat. No. 4,022,065 to Ramin et al. These devices, however, are difficult to automate because the syringe has to be flushed several times between each injection in order to eliminate cross contamination.
Probe-In-Loop (PIL) automatic samplers were consequently developed which placed a docking port and needle probe intermediarily in the sample loop. This probe was adapted to undock from the docking port to aspirate a discrete volume of sample from a source into one portion of the sample loop, and then dock with the docking port to dispense this discrete volume into the other portion of the sample loop. These xe2x80x9cPartial-Loop Injectionxe2x80x9d designs are advantageous to aspirate and dispense very small samples ( less than 1 xcexcl) with low dispersion. Further, unlike the xe2x80x9cComplete-Loop Injectionxe2x80x9d designs, the probe tip of the PIL design may be easily undocked from the docking port for cleaning thereof to prevent cross-contamination. Typical of these PIL automatic samplers are disclosed in U.S. Pat. No. 4,242,909 to Gundelfinger, and European Patent No. EP327,658 to Strohmeier.
While these PIL automatic sampler designs provide the benefits of zero sample loss and rapid change of sample injection volume without any hardware changes, the injection volumes are relatively small. Moreover, the volumetric precision of the xe2x80x9cPartial-Loop Injectionxe2x80x9d designs (typically in the range of 0.1-2.0% RSD), while good, is not as high as that of the xe2x80x9cComplete-Loop Injectionxe2x80x9d designs.
Accordingly, it would be desirable to provide a PIL automatic sampler design which enables both Partial-Fill and Complete-Fill injections.
The present invention provides a multi-function valve apparatus for use with a Probe-In-Loop (PIL) architecture sample injection assembly, having a metering pump and an injection pump. The injection pump is configured to direct a Partial-Fill or a Complete-Fill of sample into a sample loop assembly, and to inject the sample from the sample loop assembly into an analyzing device. The sample loop assembly includes an upstream loop portion having one end connected to the valve and the other end coupled to a probe. The probe is adapted to aspirate a sample and hold it or to dispense the sample into a dock. The sample loop assembly further includes a downstream loop portion having an interior volume between the end coupled to the valve and the end coupled to the dock. The valve apparatus includes a stator element having a stator face defining a metering port fluidly coupled to the metering pump. The stator face further includes an injection pump port fluidly coupled to the injection pump, a loop upstream port fluidly coupled to one end of the upstream loop portion, and a loop downstream port fluidly coupled to one end of the downstream loop portion. An exit port is further provided fluidly coupled to the analyzing device. A waste port is coupled to a waste container. A rotor having a rotor face is included in fluid-tight contact against the stator face. The rotor face includes a first bridge channel, a second bridge channel defining a discrete volume with the stator face, and a third bridge channel.
The rotor face is rotatable about a rotation axis relative the stator between: a Load Position, an Overfill Position, and an Injection Position. In the Load Position, the first bridge channel fluidly couples the metering port to the sample loop upstream port enabling the probe to aspirate a discrete volume of sample into the probe, during a Partial-Fill Mode, and a second volume of sample into the probe, during a Complete-Fill Mode. In the Overfill Position, in the Complete-Fill Mode, the second bridge channel fluidly couples the sample loop downstream port to the waste port, and the first bridge channel fluidly couples the metering port to the sample loop upstream port. This enables the metering pump, when the probe is docked in the dock, to dispense the sample from the probe into the downstream loop portion, out of the downstream port, into the second bridge channel and out the waste port to completely fill the downstream loop portion and the second bridge channel with a substantially precise known volume. Finally, in the Injection Position, the second bridge channel fluidly couples the downstream loop port to the exit port, and the third bridge channel fluidly couples the injection pump port to the sample loop upstream port. This enables the injection pump, when the probe is docked in the dock, in both the Partial-Fill Mode and the Complete-Fill Mode, to inject the sample into the analyzing device.
Accordingly, a rotor valve assembly is provided for a Probe-In-Loop automatic sampling device which enables both Partial-Fill and Complete-Fill injections. Thus, this versatile automatic sampling device enables rapid change of injection volume with zero sample loss and without any hardware changes (i.e., xe2x80x9cPartial-Loop Injectionxe2x80x9d designs), while further offering larger injection volumes with increased volumetric precision (i.e., xe2x80x9cComplete-Loop Injectionxe2x80x9d designs).
In one embodiment, the waste port, the upstream port and the exit port lie on a first imaginary circle that is concentric with the rotation axis. The distal ends of the second bridge channel further lying on the imaginary circle such that, in the Overfill Position, one distal end fluidly connects to the waste port and the other distal end fluidly connects to the loop downstream port, and such that, in the Injection Position, the one distal end fluidly connects to the loop downstream port and the one distal end fluidly connects to the exit port.
In another embodiment, the stator face further defines a first communication channel having one end in fluid communication with the exit port and the other distal end lying on the first imaginary circle such that, in the Injection Position, the other end being in fluid communication with the other end of the second bridge channel. Further, the third bridge channel fluidly couples the injection pump port to the exit port enabling the injection pump to purge the analyzing device in a fourth valve position.
In yet another configuration, in a fifth valve position, the first bridge channel fluidly couples the metering port to a pump seals port to fluidly couple the metering pump to the pump seals of the injection pump for cleaning thereof. The metering port is centrally positioned substantially at the rotational axis, and the first bridge channel extends radially outward from the rotational axis. At the same time, the third bridge channel connects the injection pump port to the waste port, allowing the pump to dump its contents to waste.
In another aspect of the present invention, a Probe-In-Loop (PIL) architecture sample injection assembly is provided comprising a rotor valve assembly including a stator element and a rotor element. The stator element includes a stator face defining an injection pump port, a metering port, a loop upstream port, a loop downstream port, an exit port and a waste port. The rotor element includes a rotor face in fluid-tight contact against the stator face, and defines at least one bridge channel. The sample injection assembly further includes an injection pump fluidly coupled to the stator injection pump port for supplying mobile phase fluid, and a metering pump fluidly coupled to the stator metering port for supplying or withdrawing metered mobile phase fluid. An analyzing device is fluidly coupled to the stator exit port. A PIL sample loop is included having a docking station, a probe, an upstream loop portion and a downstream loop portion. The upstream loop portion is fluidly coupled to the loop upstream port of the stator element to permit aspiration of sample into the probe and dispensing of the aspirated sample from the probe into the dock. The downstream loop portion fluidly couples to the dock and to the loop downstream port of the stator element. The downstream loop portion has a discrete interior volume between the dock and the loop downstream port.
The rotor face is rotatable about a rotation axis relative to the stator between: a Load Position, an Overfill Position, and an Injection Position. In the Load Position, the metering port is fluidly coupled to the sample loop upstream port enabling the probe to aspirate a discrete volume of sample into the probe, during a Partial-Fill Mode, and a second volume of sample into the probe, during a Complete-Fill Mode. In the Overfill Position, in the Complete-Fill Mode, the sample loop downstream port is fluidly coupled to the waste port, and the metering port is fluidly coupled to the sample loop upstream port. This enables the metering pump, when the probe is docked in the docking station, to dispense the aspirated sample from the probe into the downstream loop portion, and out of the loop downstream port toward the waste port to completely fill the downstream loop portion with a substantially precise known volume. In the Injection Position, the sample loop downstream port is fluidly coupled to the exit port, and the injection pump port is fluidly coupled to the sample loop upstream port. This enables the injection pump, when the probe is docked in the dock, in both the Partial-Fill Mode and the Complete-Fill Mode, to inject the sample into the analyzing device.
The rotor valve assembly of the sample injection assembly includes a seal purge position which provides purging of the seals of the injection pump. Debris and other contaminants reducing seal longevity may be swept out of the chamber behind the rear seal by this function. Preferably, in the purge position, the metering device is fluidly coupled to this chamber of the injection pump for purging thereof.
In another aspect of the present invention, a method is provided for transferring sample from a sample source to an analyzing device using multi-function valve apparatus for use with a Probe-In-Loop (PIL) architecture sample injection assembly to direct a Partial-Fill or a Complete-Fill of the sample into a sample loop assembly, and to inject the sample from the sample loop assembly into the analyzing device. The method includes loading a discrete volume of sample through the probe, in the Partial-Fill Mode, and a second volume of sample through the probe, in the Complete-Fill Mode. In the Complete-Fill Mode when the probe is docked in the dock, fluidly coupling the sample loop downstream port to the waste port through the second bridge channel of the rotor. Then, dispensing a portion of the sample from the probe though the dock and into the downstream loop portion, out of the downstream port, into the second bridge channel and out the waste port to completely fill the downstream loop portion and the second bridge channel with a substantially precise known volume. The rotor then fluidly couples the sample loop downstream port to the exit port. Finally, injecting the discrete volume of sample, in the Partial-Fill Mode, or injecting the precise known volume of sample, in the Complete-Fill Mode, into the analyzing device.